In a simulated runoff vote, the poll found Haddad would get 45 percent voter support, beating Bolsonaro with 39 percent, with the rest of those asked saying they were undecided or would annul their ballot. Voting is compulsory in Brazil.

A second-round is required if no candidate wins a majority in the Oct. 7 first ballot, which is expected to happen.

Bolsonaro, who has been hospitalised since being stabbed in a Sept. 6 assassination attempt, remained the leader in simulated first-round voting, taking 28 percent voter approval, as he did in a Sept. 20 Datafolha poll. Haddad took 22 percent, an increase of 6 percentage points.

Datafolha surveyed 9,000 voters across Brazil from Wednesday through Friday. The poll, published by the newspaper Folha de S.Paulo, has a margin of error of 2 percentage points.

Haddad earlier this month replaced jailed former president Luiz Inacio Lula da Silva, a founder of the PT and who remains Brazil’s most popular politician. He handpicked Haddad to stand in his place and polls show he is successfully transferring his support.

Haddad, a former mayor of Sao Paulo, has pledged to govern in a pragmatic fashion, but his rise has spooked markets and sent Brazil’s currency towards historic lows.

Bolsonaro, a former army captain who favours easing gun controls, shot ahead early in the race by tapping the anger of Brazilians fed up with political corruption and rising crime.

The most divisive election since the end of Brazil’s military rule three decades ago has become increasingly polarized between right and left, raising concerns about the future of the country’s democracy.

Bolsonaro, an admirer of Brazil’s 1964 to 1985 military regime, has accused the Workers Party of trying to rig the elections. His running mate, retired General Hamilton Mourão, has said the armed forces should carry out a coup if the country’s judiciary cannot end political corruption.